Despite vocal protestations when states are spied upon, current international relations literature does not explain why states do not formally regulate peacetime espionage. In this paper, I argue that states do not regulate peacetime espionage through formalized international law for five main reasons: (1) lack of enforceability, (2) regulation of high-stake security issues like being spied upon by another state will create a very short shadow of the future, (3) espionage is very closely linked to state security and survival and therefore the penalty for unilateral cooperation is very high if the other party defects, (4) formal regulation would affect stronger states differently than weaker states, and (5) states recognize the benefits of tolerating some forms of relatively benign spying on themselves during peacetime because of the general recognition that reducing private information -- including that related to misunderstood intentions -- contributes to stability.

I argue that since espionage allows states to determine and verify the intentions of other states and that knowing the intentions of other states builds trust and cooperation, espionage is thus an instrument for stability and peace. I conclude that because any attempt at regulating espionage would remove this tool of states to determine actual intentions, any formal regulation of peacetime espionage would breed distrust, misunderstanding, and destabilization of the current relationship between states.